Due to international terrorism and other crime related threats, law enforcement and homeland security forces are always in seek for improved detection methods and devices which will allow them to more securely and effectively cope with such threats. Improvements in the existing devices and methods, as well as the provision of new devices and methods, are generally directed towards one or more of the following benefits: reducing the costs involved in equipping law enforcement manpower with appropriate detection devices, increasing the reliability of detection, reducing the time to be invested in a checking event, reducing the level of expertise required for carrying out the checking procedure and making it more comfortable for decent persons who may undergo screening procedures due to strict security demands.
The devices currently available for detection of trace explosives/narcotics and gunshot residues are of one of the two following main categories: (i) devices called sniffers, which are vapor detection devices, specializing in automated analysis of trace explosives/narcotics in the form of vapors. Such vapors may be present in the atmosphere of a detected region before being collected into a computerized analyzing unit by suction (i.e. collection by a vacuum or vacuum vortex system), or may be prepared for the analysis from sampled particles by heating them for evaporation thus allowing delivery of the vapors released from the particles into the computerized analyzing unit by suction; and (ii) chemical kit devices for particles detection, for identification of potential threats according to color changes in chemical reactions visually identifiable by a user when a particle of interest, drug or explosive, reacts with preprepared chemical reagents provided as part of the kit.
Generally, vapor detection methods are orders of magnitudes more sensitive comparing to visual detection of color changes in chemical reactions (nanograms to picograms detection sensitivity in vapor detection methods comparing to micrograms to nanograms detection, sensitivity in color chemically based detection methods, depending on the particular substance examined). Such extraordinary sensitivity of vapor detection methods may be considered advantageous in some aspects, however several drawbacks may be associated with the vapor detection approach:                i. The technologies underlying vapor detection are highly expensive. Mobile device such as QS-H150™ or Sabre 5000™ of Smithdetection™ are priced in the range of tens of thousands US dollars, thus are financially affordable only for special check spots, such as air ports and border terminals, while small terminals, police patrol vehicles and the like are equipped with chemical test kits.        ii. The extremely high sensitivity of vapor detection devices exposes them to operation interruptions due to possible self contamination. It is expected that even a small particle of illicit drugs or explosives which incidentally may happen to cross the filtering system of the device will cause it to maintain either a constant or an unexpectedly repeating false positive alarm due to the vapors released from the particle. It can take some hours for a trained person to dismantle the device, clean it and return it to normal operation.        iii. Low vapor pressure explosives like PETN or RDX have equilibrium vapor concentration in air of as low as near one part per trillion (1 ppt) level, which \ vapor detection are incapable of effectively recognize detection        iv. About 1% of false positive detection is expected in normal operation of vapor detection devices, according to manufacturer's specifications.        In view of these, when screening events are occasional, random, or in moderate numbers, particle detection by color change of a chemical reaction is advantageous in terms of both price and reliability, when referring to trace explosives/narcotics detection directed to suspected people, cars, baggage and the like. Particles detection is disadvantageous however in terms of sample collection efficiency.        
The main problems associated with sample collection of trace particles of explosives and narcotics are discussed in the background chapter of U.S. Pat. No. 7,574,930. This document also distinguishes between a contact sample collection procedure in which sample is collected from the suspected object by wiping, and between a non-contact particles collection procedure in which a sample is collected by vacuum or by vacuum vortex based collecting means. It is understood from the background of said patent that due to possible strong surface adhesion forces of explosives and narcotics, the power of the air flow applied to a target surface by vacuum and vacuum vortex collection methods is insufficient to remove particles of explosives and narcotics from rigid surfaces, unless the collection method is successfully improved as suggested in the specification of said U.S. patent.
It can be appreciated accordingly, that the most reliable method for particles collection of explosives and narcotics is by wiping. Disadvantageously, however, sampling by wiping is (i) time consuming when applied to large surface areas, and (ii) is considered uncomfortable and invasive when applied to a person's body and clothing.
Successful application of the improvements of the sampling device suggested by U.S. Pat. No. 7,574,930 may improve the efficiency of particle sampling for chemically based color test, with the price of reducing the reliability of a test due to potential contamination of a current test by traces of substances of interest acquired by the suction device in previous tests. While computerized sniffers may comply with this problem by self calibration of the device as a preparation step to be taken before every new sampling, chemically based test kits for color change detection are unable to distinguish between a particle of interest acquired during a current sampling event and between contamination of the current test by previously acquired traces of materials. The device suggested by U.S. Pat. No. 7,574,930 is thus not sufficiently reliable for chemical tests.
Chemically based detection is thus commonly based on suspected particles collection by wiping, e.g. as suggested by the following patents.
A chemical kit device for particle detection by wiping is disclosed by WO2006093517 titled spot test kit for explosives detection. The kit device comprises a body, a lateral flow membrane swab unit adapted to be removably connected to the body, two explosives detecting chemical reagents, two chemical reagent holders and dispensers operatively connected to the body, the two chemical reagent holders and dispensers are respectively containing the two explosives detecting chemical reagents and are positioned to deliver the explosives chemical reagents to the lateral flow membrane swab unit when the lateral flow membrane swab unit is connected to the body. The swab unit has a sample pad to be exposed to a suspect substance when the sample pad is swiped across a surface containing the suspect substance or in other ways such as adding the suspicious substance to the sample pad.
U.S. Pat. No. 7,410,612 relates to a gunpowder particle test kit for determining gunpowder traces, which includes a transparent sleeve having a closed end and an open folded end sealed with a clip forming a sealed cavity carrying a test strip and a crushable ampoule carrying a diphenylamine solution. The test strip has an adhesive area on a front surface. An opaque label is provided on a rear surface on the sleeve opposite the adhesive area. In use, the clip is removed to open the cavity, the test strip removed and applied by wiping to possible traces areas on a subject. The strip is returned to the cavity; the clip reapplied to seal the cavity. Thereafter, the ampoule is crushed to release the solution, which develops a distinctive coloration observable against the label to indicate the presence of possible gunpowder traces.
It is thus within the aims of the present invention to improve the collection method for chemically based detection of explosives/narcotics traces and gunshot residues, simplifying the preparation of a trace sampling device that will collect efficiently suspected particles and will eliminate false positives due to contamination acquired during previous tests.